Optimizing SPM Fe3O4 NPs for specific applications requires improvements in two critical areas

(1) synthesis of NPs having a large size (around 20 nm) and relatively narrow size distribution, and (2) elucidation of their structure and phase composition to determine structure−property relationships. A narrow particle size distribution around 20 nm maximizes Ms while reducing the undesirable FiM contribution of large NPs, which increases with polydispersity. The majority of the methods used to prepare Fe3O4 NPs lead to particle sizes of about 10 nm and correspondingly low Ms values, following the general particle-size dependence of Ms. 6. In contrast, Ms values are as high as 85 emu/g (at 2 K) have been achieved for larger (20 nm) NPs;7 gram-scale synthesis of such large NPs, however, is difficult.8 Large colloidal SPM Fe3O4 NPs have been prepared mainly by three routes: (1) thermal decomposition,9 (2) mild oxidation of Fe2+ precursor10 followed by stabilization of the resultant NPs in colloidal form,11 and (3) the classical synthesis of 10 nm NPs by coprecipitation followed by hydrothermal growth of the particles.12 The limited number of available synthesis methods motivates the developing of new protocols to prepare large SPM Fe3O4 NPs. Hydrophilic Fe3O4 NPs were synthesized on a large scale by controlled coprecipitation in an automated batch reactor Atlas Potassium (Syrris), equipped with two syringe pumps (Syrris), temperature control system LH85 PLUS (Julabo), overhead stirrer, as well as temperature, pH, and turbidity probes. Briefly, 40.75 mmol of FeCl2·4H2O (99%, Sigma-Aldrich) and 74 mmol of FeCl3·6H2O (99%, Sigma-Aldrich) was dissolved in a 2 L glass reaction vessel filled with 1.1 L of ultrapure water (produced by Milli-Q Advantage A10 system, Millipore) to obtain a clear orange solution. The solution was heated to 363 K, and then 60 mL of aqueous ammonia solution (28−30%, Sigma-Aldrich) was added at 10 mL/min using a syringe pump. If you are looking for high quality, high purity and cost-effective Fe3O4, or if you require the latest price of Fe3O4, please feel free to email contact mis-asia.